Install
How to install HTML Purifier
HTML Purifier is designed to run out of the box, so actually using the
library is extremely easy. (Although... if you were looking for a
step-by-step installation GUI, you've downloaded the wrong software!)
While the impatient can get going immediately with some of the sample
code at the bottom of this library, it's well worth performing some
basic sanity checks to get the most out of this library.
---------------------------------------------------------------------------
1. Compatibility
HTML Purifier is PHP 5 only, and is actively tested from PHP 5.0.0 and
up (see tests/multitest.php for the specific versions that are being
actively tested). It has no core dependencies with other libraries. PHP
4 support was deprecated on December 31, 2007 with HTML Purifier 3.0.0.
Essential security fixes will be issued for the 2.1.x branch until
August 8, 2008.
These optional extensions can enhance the capabilities of HTML Purifier:
* iconv : Converts text to and from non-UTF-8 encodings
* tidy : Used for pretty-printing HTML
---------------------------------------------------------------------------
2. Reconnaissance
A big plus of HTML Purifier is its inerrant support of standards, so
your web-pages should be standards-compliant. (They should also use
semantic markup, but that's another issue altogether, one HTML Purifier
cannot fix without reading your mind.)
HTML Purifier can process these doctypes:
* XHTML 1.0 Transitional (default)
* XHTML 1.0 Strict
* HTML 4.01 Transitional
* HTML 4.01 Strict
* XHTML 1.1
...and these character encodings:
* UTF-8 (default)
* Any encoding iconv supports (with crippled internationalization support)
These defaults reflect what my choices where be if I were authoring an
HTML document, however, what you choose depends on the nature of your
codebase. If you don't know what doctype you are using, you can determine
the doctype from this identifier at the top of your source code:
...and the character encoding from this code:
If the character encoding declaration is missing, STOP NOW, and
read 'docs/enduser-utf8.html' (web accessible at
http://htmlpurifier.org/docs/enduser-utf8.html). In fact, even if it is
present, read this document anyway, as most websites specify character
encoding incorrectly.
---------------------------------------------------------------------------
3. Including the library
The procedure is quite simple:
require_once '/path/to/library/HTMLPurifier.auto.php';
I recommend only including HTML Purifier when you need it, because that
call represents the inclusion of a lot of PHP files which constitute
the bulk of HTML Purifier's memory usage.
If you don't like your include_path to be fiddled around with, simply set
HTML Purifier's library/ directory to the include path yourself and then:
require_once 'HTMLPurifier.php';
Only the contents in the library/ folder are necessary, so you can remove
everything else when using HTML Purifier in a production environment.
---------------------------------------------------------------------------
4. Configuration
HTML Purifier is designed to run out-of-the-box, but occasionally HTML
Purifier needs to be told what to do. If you answered no to any of these
questions, read on, otherwise, you can skip to the next section (or, if you're
into configuring things just for the heck of it, skip to 4.3).
* Am I using UTF-8?
* Am I using XHTML 1.0 Transitional?
If you answered no to any of these questions, instantiate a configuration
object and read on:
$config = HTMLPurifier_Config::createDefault();
4.1. Setting a different character encoding
You really shouldn't use any other encoding except UTF-8, especially if you
plan to support multilingual websites (read section three for more details).
However, switching to UTF-8 is not always immediately feasible, so we can
adapt.
HTML Purifier uses iconv to support other character encodings, as such,
any encoding that iconv supports
HTML Purifier supports with this code:
$config->set('Core', 'Encoding', /* put your encoding here */);
An example usage for Latin-1 websites (the most common encoding for English
websites):
$config->set('Core', 'Encoding', 'ISO-8859-1');
Note that HTML Purifier's support for non-Unicode encodings is crippled by the
fact that any character not supported by that encoding will be silently
dropped, EVEN if it is ampersand escaped. If you want to work around
this, you are welcome to read docs/enduser-utf8.html for a fix,
but please be cognizant of the issues the "solution" creates (for this
reason, I do not include the solution in this document).
4.2. Setting a different doctype
For those of you using HTML 4.01 Transitional, you can disable
XHTML output like this:
$config->set('HTML', 'Doctype', 'HTML 4.01 Transitional');
Other supported doctypes include:
* HTML 4.01 Strict
* HTML 4.01 Transitional
* XHTML 1.0 Strict
* XHTML 1.0 Transitional
* XHTML 1.1
4.3. Other settings
There are more configuration directives which can be read about
here: They're a bit boring,
but they can help out for those of you who like to exert maximum control over
your code. Some of the more interesting ones are configurable at the
demo and are well worth looking into
for your own system.
For example, you can fine tune allowed elements and attributes, convert
relative URLs to absolute ones, and even autoparagraph input text! These
are, respectively, %HTML.Allowed, %URI.MakeAbsolute and %URI.Base, and
%AutoFormat.AutoParagraph. The %Namespace.Directive naming convention
translates to:
$config->set('Namespace', 'Directive', $value);
E.g.
$config->set('HTML', 'Allowed', 'p,b,a[href],i');
$config->set('URI', 'Base', 'http://www.example.com');
$config->set('URI', 'MakeAbsolute', true);
$config->set('AutoFormat', 'AutoParagraph', true);
---------------------------------------------------------------------------
5. Caching
HTML Purifier generates some cache files (generally one or two) to speed up
its execution. For maximum performance, make sure that
library/HTMLPurifier/DefinitionCache/Serializer is writeable by the webserver.
If you are in the library/ folder of HTML Purifier, you can set the
appropriate permissions using:
chmod -R 0755 HTMLPurifier/DefinitionCache/Serializer
If the above command doesn't work, you may need to assign write permissions
to all. This may be necessary if your webserver runs as nobody, but is
not recommended since it means any other user can write files in the
directory. Use:
chmod -R 0777 HTMLPurifier/DefinitionCache/Serializer
You can also chmod files via your FTP client; this option
is usually accessible by right clicking the corresponding directory and
then selecting "chmod" or "file permissions".
Starting with 2.0.1, HTML Purifier will generate friendly error messages
that will tell you exactly what you have to chmod the directory to, if in doubt,
follow its advice.
If you are unable or unwilling to give write permissions to the cache
directory, you can either disable the cache (and suffer a performance
hit):
$config->set('Core', 'DefinitionCache', null);
Or move the cache directory somewhere else (no trailing slash):
$config->set('Cache', 'SerializerPath', '/home/user/absolute/path');
---------------------------------------------------------------------------
6. Using the code
The interface is mind-numbingly simple:
$purifier = new HTMLPurifier();
$clean_html = $purifier->purify( $dirty_html );
...or, if you're using the configuration object:
$purifier = new HTMLPurifier($config);
$clean_html = $purifier->purify( $dirty_html );
That's it! For more examples, check out docs/examples/ (they aren't very
different though). Also, docs/enduser-slow.html gives advice on what to
do if HTML Purifier is slowing down your application.
---------------------------------------------------------------------------
7. Quick install
First, make sure library/HTMLPurifier/DefinitionCache/Serializer is
writable by the webserver (see Section 5: Caching above for details).
If your website is in UTF-8 and XHTML Transitional, use this code:
purify($dirty_html);
?>
If your website is in a different encoding or doctype, use this code:
set('Core', 'Encoding', 'ISO-8859-1'); // replace with your encoding
$config->set('HTML', 'Doctype', 'HTML 4.01 Transitional'); // replace with your doctype
$purifier = new HTMLPurifier($config);
$clean_html = $purifier->purify($dirty_html);
?>